Corrosion inhibited paint removing composition

ABSTRACT

A paint-removing formulation comprising a mixture of: sodium metasilicate pentahydrate, trisodium phosphate dodecahydrate, monosodium phosphate monohydrate, dodecylbenzene sodium sulfonate in conjunction with a small amount of an inhibitor consisting of sodium stannate tetrahydrate or potassium stannate tetrahydrate. In the alternative, the anhydrous forms of the above components may be utilized.

United States Patent Myer Rosenfeld Baltimore;

Troy R. Nichols, Bel Air, both of Md. 881,266

Dec. 1, 1969 Dec. 7, 1971 The United States of America as represented by the Secretary of the Army inventors Appl. No. Filed Patented Assignee CORROSION INHIBITED PAINT REMOVING COMPOSITION 8 Claims, No Drawings U.S. Cl 252/138, 23/53,117/130,134/38,148/6.27, 252/135, 252/156, 252/387, 252/389, 252/D1G. 8

Int. Cl C09d 9/04, C23f 1 1/18 Field of Search 252/135,

References Cited UNITED STATES PATENTS 11/1965 Mankowich 252/111 3,034,210 5/1962 De Long 252/389 X 2,947,639 8/1960 Balden 117/130 X 2,898,246 8/1959 Hannah 1. 252/156 X 2,822,325 2/1958 Tinnon et a1.. 204/54 L X 1,939,421 12/1933 Tosterud 148/627 X OTHER REFERENCES Protective Coatings for Metals," by R. M. Burns & W. W. Bradley, 2nd Ed., 1955, pages 156 & 165. The Chemical Formular, V01. X111, by H. Bennett, 1967, Page 195.

Primary Examiner- Leon D. Rosdol Assistant E.taminerDennis L. Albrecht Attorneys-Harry M. Saragovitz, Edward J. Ke11y and Herbert Berl CORROSION INHIBITED PAINT REMOVING COMPOSITION The invention described herein may be manufactured, used,

formulations set forth in table I below for a period of I hour. The panels were then removed from the test solution, rinsed under flowing tap water, dipped into absolute ethyl alcohol and dried with paper toweling. To remove any residual film and licensed by or for the Government for governmental purthat had formed during the test, the panels were immersed in poses without the payment to us of any royalty thereon. concentrated nitric acid at room temperature for 2 minutes. This invention relates to a composition having utility in the The panels were then rinsed thoroughly under flowing tap removal of paints from metals. More particularly, it relates to water, dipped into absolute ethyl alcohol, dried with paper the inclusion of a small amount of sodium or potassium toweling. and weighed to 0.0001 grams. The difference in stannate in a metal paint-removing composition to inhibit the weight of the panel after treatment represents loss due to corcorrosion of aluminum or alloys thereof. rosion. it was found that the average weight loss due to the Sodium or potassium chromates are usually utilized in paint treatment of the panels with nitric acid after immersion of the removing formulations to inhibit the corrosion of the metal. panels in the cleaning formulation was around 0.05 mg. However, the disposal of waste chromates constitutes a The paint removing composition evaluated in this invention problem in that soluble chromates are poisonous. Acl5 consisted of an alkali-type formulation for hot application cordingly, many municipalities severely limit the chromium composed of: sodium metasilicate pentahydrate, trisodium concentration permitted to enter effluent streams or waterphosphate dodecahydrate. monosodium phosphate ways. The allowable hexavalem h mi on t t monohydrate and dodecylbenzene sodium sulfonate. A corrogested by the U.S. Public Health Service for the protection of sion inhibitor consisting of sodium stannate tetrahydrate, fish is 0.50 milligrams per liter for industrial waste effluent 2 potassium stannate tetrahydrate or potassium chromate was after mixing with receiving water. Therefore, it i oft n e utilized. illustrative examples of the present formulation are sary to dilute the waste containing chromate to a permissible set forth in table I below. The ingredients in said table I are level prior to discharging into effluent streams or waterways. calculated on the basis of their hydrated and anhydrous forms. When appreciable concentrations of chromates are needed The utilization of an alkali cleaner without the inclusion of for corrosion inhibition, this becomes a lengthy operation. any corrosion inhibitor therein (formulation 1) resulted in an TABLE 1 Formulation 1 2 3 4 5 6 7 8 9 10 Composition (percent by weight):

Sodium metasilicate, pentahydrate 35.08 35.07 35.04 35.07 34. 31 34. 69 31.69 35.07 35.07 35.01 Trisodium phosphate, dodecahydrat 47.87 47.83 47. 87 46. 84 47. 36 47.30 47.87 47.87 47.79 Monosodium phosphate. monohydra 12.02 12.01 12.02 11.77 11.80 11.89 12.02 12.02 12.00 Dodecylbenzeue sodium sultonate, 86% active 5.01 5.01 5.01 5.01 4.00 4 96 4 96 5.01 5.01 5.00 Sodium stannate tetrahydrate 0.03 0.11 Potassium stannate tetrahydrate. Potassium chromate Paint remover, g./100 ml. aqueous solution:

Sodium metasilicate, peutahydrate 3.15 3.15 3.15 'Irisodlum phosphate, dodecahydrate... 4. 4.30 4.30 Monosodium phosphate, monohydrate 1. 08 1.08 1.08 Dodecylbenzene sodium sultonate, 86% active. 0. 0.45 0. 45 Sodium stannate 0.0030 0.010 Potassium stannate 00 Potassium chromate Composition (percent by weight as anyhdrous):

Sodium metasilicate 36. 30 35. 29 30. 24 36. 29 35. 24 35. 75 35.74 36. 29 Trlsodium phosphate-.. 37.14 37.13 37.00 37.14 36. 05 36.60 36. 58 37.13 Monosodium phosphate 18.81 18.79 18. 77 18.79 18.20 18. 52 18.51 18.79 Dodecylbenzene sodium sulionate, 100% active. 7.75 7.75 7. 75 7. 75 7.52 7.65 7.65 7. 75 Sodium stannate 0.04 0.15 0.027 2.03 1.48 Potassium stannate 1.52 0.04 Potassium chromate 0.05 0.30 Paairnt remover. g./100 m1. aqueous solution (as anhyans 1 Sodium metasilicate 1.81 1.81 1.81 1.81 1.81 1.81 1.81 1.81 1. 81 1. 81 Trisodium phosphate. 1. 85 1.85 1.85 1.85 1.85 1. 85 1.85 1.85 1.85 1.85 Monosodium phosphate 0. 9 0. 94 0. 94 0. 94 0. 94 0. 94 0. 94 0.04 0.94 0.04 Dodeeylbenzene sodium sultonate, 100% active. 0. 39 0.39 0. 30 0.39 0. 39 0.39 0.30 0. 30 0. 30 0. 30 Sodium stannate .00215 0075 .0015 0.15 0.075

Potassium stannate Potassium chromate Corrosion (aluminum 28), average weight loss, mg..

It is an object of this invention to provide and disclose a paint-removing composition including a metal-corrosion inhibitor.

It is a further object of this invention to provide and disclose a corrosion inhibitor which is nontoxic to wildlife when discharged in effluent streams and waterways.

Other objects and a fuller understanding of the invention may be had by referring to the following description and claims.

The ability of the present sodium or potassium stannate containing paint removing formulation to inhibit corrosion was evaluated by subjecting metal test panels to the action thereof. Four panels were utilized in the evaluation of each formulation and an average result calculated therefrom. The test panels utilized, which have dimensions of three-fourths inch by 3 inches and a thickness of approximately 0.030 inch, were cut from 28 aluminum (aluminum alloy SAE-AAl 100). The panels were cleaned by lightly polishing with No. I Alundum paper, washed with acetone, wiped with paper toweling, dipped into absolute ethyl alcohol and again wiped with paper toweling. After' being weighed to 0.0001 grams, the

test panels were immersed in a boiling aqueous solution of the adequate to inhibit corrosion. Formulation l0 discloses that 0.20 percent by weight of potassium chromate is essential in order to provide proper corrosion inhibition. This compares with .03 percent by weight of sodium or potassium stannate tetrahydrate.

Although we have described out invention with a certain degree of particularity, we wish it to be understood that we do not desire to be limited to the exact details of formulations shown and described, for obvious modification will occur to a person skilled in the art.

Having described our invention, we claim:

1. A paint stripping composition consisting essentially of about: 34.69-35.07 percent sodium metasilicate pentahydrate; 47.36-48.87 percent trisodium phosphate dodecahydrate;

ll.89-l2.02 percent monosodium phosphate monohydrate; 46.96-5.0l percent dodecylbenzene sulfonate and a corrosion inhibitor in an amount of about 0.03-l.l percent selected from the group consisting of potassium and sodium stannate, all amounts being on a weight basis.

2. An aqueous solution of the composition of claim 1 consisting of about 8.98 to 9.08 grams of composition per 100 ml. of solution.

3. An aqueous solution in accordance with claim 1 wherein the corrosion inhibitor is sodium stannate tetrahydrate in an amount of 0.003 to 0.10 grams per I00 ml. of solution.

4. An aqueous solution in accordance with claim 1 wherein the corrosion inhibitor is potassium stannate tetrahydrate in an amount of 0.003 to 0.10 grams per 100 ml. of solution.

5. A pain stripping composition consisting essentially of about: 35.75-36.29 percent sodium metasilicate; 36.60-37.09 percent trisodium phosphate; 18.52-18.79 percent monosodium phosphate; 7.65-7.75 percent dodecylbenzene sodium sulfonate, and a corrosion inhibitor in an amount of about 0.04-1.52 percent selected from the group consisting of potassium and sodium stannate, all amounts being on a weight basis.

6. An aqueous solution of the composition of claim 5 consisting of 5.19-5.30 grams of composition per 100 ml. of solution.

7. An aqueous solution in accordance with claim 5 wherein the corrosion inhibitor is sodium stannate in an amount of 0002-0075 grams per 100 ml. of solution.

8. An aqueous solution in accordance with claim 5 wherein the corrosion inhibitor is potassium stannate in an amount of 0002-0077 grams per 100 ml. of solution. 

2. An aqueous solution of the composition of claim 1 consisting of about 8.98 to 9.08 grams of composition per 100 ml. of solution.
 3. An aqueous solution in accordance with claim 1 wherein the corrosion inhibitor is sodium stannate tetrahydrate in an amount of 0.003 to 0.10 grams per 100 ml. of solution.
 4. An aqueous solution in accordance with claim 1 wherein the corrosion inhibitor is potassium stannate tetrahydrate in an amount of 0.003 to 0.10 grams per 100 ml. of solution.
 5. A pain stripping composition consisting essentially of about: 35.75-36.29 percent sodium metasilicate; 36.60-37.09 percent trisodium phosphate; 18.52-18.79 percent monosodium phosphate; 7.65-7.75 percent dodecylbenzene sodium sulfonate, and a corrosion inhibitor in an amount of about 0.04-1.52 percent selected from the group consisting of potassium and sodium stannate, all amounts being on a weight basis.
 6. An aqueous solution of the composition of claim 5 consisting of 5.19-5.30 grams of composition per 100 ml. of solution.
 7. An aqueous solution in accordance with claim 5 wherein the corrosion inhibitor is sodium stannate in an amount of 0.002-0.075 grams per 100 ml. of solution.
 8. An aqueous solution in accordance with claim 5 wherein the corrosion inhibitor is potassium stannate in an amount of 0.002-0.077 grams per 100 ml. of solution. 